Raisins have long been a popular and widely used food, either alone as a snack food, as toppings on cereals or mixed with other foods to form salads, or in cooked or baked food preparations such as puddings, cakes, cookies and bread. While appealing taste and nutritional value are among the most desirable assets of raisins, the industry has found it beneficial to treat raisins in various ways and to impose certain restrictions on them to prolong their texture and retard spoilage. Factors adverse to their appeal which these methods and restrictions are intended to address are the formation of crystals (hydrates of glucose, fructose and sucrose as well as potassium bitartrate, the crystal formation known in the industry as "sugaring"), and the occurrence of fermentive spoilage and mold spoilage. California Thompson Seedless raisins, for example, are subject to a maximum moisture level of 18% by weight for purposes of avoiding sugaring and spoilage. Muscats are subject to a maximum of 19%. Zante currants are subject to a maximum of 20%. Other varieties are subject to similar maxima.
When raisins are used in commercial food preparations, however, such as baked goods, confections, and dairy products, a higher moisture content is preferred. This prevents the drying and hardening of the raisins during either the preparation or the storage of the food product. These problems are particularly prominent in bakery operations. To avoid these problems, the raisins are preconditioned to raise the moisture level, generally to about 25%, corresponding to a water activity of 0.65 or higher. To achieve this without reintroducing the risk of sugaring or spoilage, the conditioning is done on site where the final product is produced. For baked goods, for example, conditioning is performed at the bakery operation prior to combining the raisins with the other baking ingredients. The common method of conditioning is to place raisins having moistures in the range of 14% to 18% in tubs or troughs, covering the raisins with water at 60.degree. F. to 70.degree. F. (16.degree. C. to 21.degree. C.), soaking for 10 to 60 minutes, then draining the raisins for 60 minutes or more.
Drawbacks of this conditioning process are that it is cumbersome and time-consuming, and that the resulting raisins lack uniformity, displaying a wide range of moisture levels and other properties. Excessive exposure to water during attempts to moisturize weakens the skins of the raisins, thereby increasing their susceptibility to bursting. Excessive exposure to water also leaches sugars from the raisins, which causes a loss of taste appeal and a dilution of the dark brown color which is characteristic of raisins. The dark brown color is particularly important to visual appeal when the raisins are used in baking, since it enhances the contrast between the raisins and white flour. High moisture levels also run a risk of unwanted levels of microbial growth in the raisins, when raisins are preconditioned to a high moisture level and then stored. Microbial growth cannot be controlled by treatment with antimicrobials, since the retention of antimicrobials in the final baked goods would be undesirable from a potential toxicity standpoint, and antimicrobials retard the action of yeast, thereby interfering with baking. A further reason not to use antimicrobials is that they would detract from the natural foods character of the raisins. As mentioned above, if the moisture level of raisins used in baking with dough is too low, the raisins tend to draw moisture from the remaining ingredients of the food product. In baked products, for example, the remaining ingredient is dough, whereas in dairy products, the remaining ingredient is ice cream, cream cheese or whatever other type of dairy product is being prepared. In each case, the resulting food product is drier, and in the case of baked goods, the goods will have a texture gives the impression of being less fresh. Even when the product has a fresh-appearing texture after baking, the product will generally have a relatively short shelf life.
With these variations in the moisture level of raisins used in baked, dairy or other food products whose texture, appearance and mouthfeel are affected by moisture content, the result is a lack of control over the quality of these products when raisins are incorporated. The present invention addresses these and other problems.